This invention relates to new and useful improvements in survey methods for radon and although designed basically for the surveys of radon in soil, nevertheless it is readily adapted for use for the survey of airborne radon as will hereinafter be described. It includes the sampling apparatus and the scintillation cell and the method of using same.
Conventionally, the abundance of radon in soil is determined by using standard radon sniffers, buried alpha deflectors and the like.
These suffer from several disadvantages given below:
Firstly, there is a serious contamination of the scintillation chamber after each sample which becomes increasingly severe over a series of samples, to the point where the contamination count may even exceed the count due to radon. This makes the radon sniffer an inherently very inaccurate instrument.
Secondly, very long waiting times are required (15 minutes is not uncommon) between samples for flushing radon from the chamber and to allow the instrument to decontaminate in order to minimize the above disadvantage. This severely diminishes the productivity of the instrument.
Thirdly, at least two successive counts of at least one minute each are required to adequately distinguish radon from thoron which is also abundant in some areas. The long residence time of radon in the scintillation chamber aggravates problem above.
Fourthly, the hand pump normally used, is a frequent source of error. It can fail to perform its function adequately without the knowledge of the operator.
The combined effect of these problems makes the sniffer a difficult and unreliable instrument, particularly for small amplitude anomalies.